In a wireless communications system, an uplink channel between a remote station and a base station has a received signal parameter value (e.g., signal strength) that depends upon the location of the remote station relative to the base station. In a time-division multiplex communications system, multiple uplink channels may be used simultaneously. The dynamic range of a coverage area represents a range from a lowest received signal strength of one channel to a highest received signal strength of another channel. For example, the lowest received signal strength may be a result of a remote station located at a periphery of the coverage area in which a base station is centrally located. The coverage area may be defined in terms of a probability of providing an electromagnetic transmission of at least a target minimum signal strength between a base station and a remote station throughout a cell, or sector thereof.
In a time-division multiplex wireless system, a wide dynamic range within a coverage area may impede the ability of the base station to adjust downlink transmit power transmitted to remote stations. A group of channels may be organized in such a manner as to limit the channels to a constant downlink transmit power, regardless of an uplink signal strengths or locations of the remote stations in the coverage area. However, the inability to adjust downlink transmit power in a time-division multiplex communications system may reduce the traffic capacity of a wireless communications system. Thus, a need exists for enabling downlink power control in coverage areas with potentially wide dynamic ranges of received signal strengths to realize the full potential capacity of a wireless system.
In some applications, a wide dynamic range of signal strength creates stringent isolation requirements in base station receiver circuitry. For example, a receiver may group channels from different frequency groups for input into a common intermediate frequency circuit module. The common intermediate frequency circuit module requires a degree of isolation that generally increases as the dynamic range of received signal strengths within a coverage area increases. Adequate isolation within the module prevents a "loud" channel with a higher signal magnitude from overwhelming and interfering with a "quiet" channel with an appreciably lower signal magnitude. While radio frequency shielding may sometimes provide adequate radio frequency isolation between circuit components, maximum achievable circuit board density may be sacrificed to accommodate metallic forms for shielding. Further, radio frequency shielding may involve burdensome redesigns of the metallic forms and testing of circuit boards after each modification of a circuit board. Thus, a need exists for reducing the radio frequency isolation requirements for receiver circuitry of communication system applications.